1. Field of the Invention
The present invention relates to devices for lifting and lowering objects, and more particularly to light-weight jacks adaptable for use in a laboratory environment.
2. Description of the Prior Art
Prior art discloses many devices and mechanisms for raising and lowering heavy objects. Many such devices are constructed of metal, however, utilization of metallic jacks in the laboratory environment has substantial drawbacks. It is known that metal can be expensive because of the fabrication and assembly expense. Significantly, metals, particularly relatively inexpensive metals, have a tendency to corrode. This is unacceptable in the laboratory environment, where corrosion might affect the results of the conducted experiments. Furthermore, corrosion might affect the mechanisms of the jacks by interfering with relative movement between working parts. Still further, metallic jacks are known to be heavy and relatively difficult to operate, especially in limited confinement areas of many laboratories.
Low weight jacks made of non-metallic materials are also known in the art. However, such lifting devices have not been very successful for a number of reasons. Typically, their structural elements have not been developed in a manner to utilize plastic materials, while being strong enough to lift heavy objects and maintaining a small size. A great majority of non-metallic jacks are replicas of their traditional metallic counterparts. One drawback in adapting existing metallic structures to plastic construction is that the standard metal jacks are better able to withstand the gravitational, bending and torsion forces and momentums to which the jacks are exposed. Many non-metallic jacks of the prior art do not contain strengthening or reinforcing elements especially provided to resist such forces and momentums.
The prior art non-metallic jacks typically suffer from such major drawbacks as a limited collapse of their structure due to applying loads or pressures in a substantially vertical directions and undesirable movement or wobbling and/or dislocation of the structural element as a result of off-center forces applied to the jack. The latter drawback often causes the inability to maintain scissor sub-assemblies parallel to each other and maintaining the load-bearing platform to be oriented in a plane parallel to the base throughout the operation of the jack.
Another drawback of non-metallic jacks of prior art made of plastic materials is the relative complexity of structures as they contain many parts. In this manner, an expensive mold is often required for production of each and every part of the assembly, ultimately increasing the cost of manufacturing of the non-metallic jack.
Thus, there has been a long-felt unsolved need to provide a non-metallic laboratory jack which is relatively inexpensive, non-corrosive, and does not alter results of laboratory experiments. There is also a need for an inexpensive jack which is made by utilizing a limited number of standardized parts. Furthermore, there has been a need for such a laboratory jack of non-metallic construction which is specifically adapted to withstand bending, torsion, and momentums found during regular use.